Chinese search engine Baidu has fired four employees, three of whom are now under arrest, for allegedly accepting bribes to delete content on its popular online forum, a practice the company said was part of a "major problem" facing the country's Internet.

Baidu discovered the employees' "suspicious behavior" after a recent crackdown on illegal online post deletion, the company said in a statement on Tuesday. Baidu then reported the activities to the authorities, which led to the arrest of the three employees. A fourth employee was stopped by the company before "any major damage" had been done, but fired for violating ethic practices, said Baidu spokeswoman Betty Tian.

The content deletion occurred on the company's online forum, Baidu Tieba, where users can search and create new discussion topics. Baidu said it will not accept any payment in handling online user complaints, adding that the company monitors employees with authority to delete such posts.

"Baidu will crack down on any illegal post deletion behavior upon discovery without hesitance. Illegal post deletion is a major problem for the Chinese Internet," the company said in its statement.

Companies including Baidu are required to obey China's strict censorship laws, which can result in the filtering out of anti-government content. But in addition to this, an online industry has emerged in the country, offering paid services to users wanting to delete sensitive content from prominent websites.

Although it was unclear what content the employees had deleted from Baidu Tieba, users in China can easily search for services over the Internet that specialize in taking down controversial or negative comments on online forums. Called "professional post deleting" companies, they claim they can delete posts from Baidu Tieba, along with other Chinese sites.

One company when contacted said it could easily delete a post on Baidu Tieba, concerning pictures of faulty furnaces from a Chinese company. An employee, who declined to be named, said the company could take down the post within about 24 hours for 1,500 yuan (US$237). When asked how, the employee said the company possessed channels to make the deletion, without giving further details.

Baidu said the company is working with Chinese authorities to crack down on the practice of illegal content deletion. "Baidu will employ more rigorous administration and procedures in managing illegal post deletion to set an example for Chinese Internet companies," it added.

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